Method and apparatus for injecting contrast media into the vascular system

ABSTRACT

A method and apparatus by which fluid is delivered either sequentially at two different rates or at one rate as desired. Suitable controls are provided for independently selecting such different flow rates and the duration of time of each flow rate, which may either be manually or automatically delivered. During the injection cycle, a slow prolonged infusion, typically 2 ml per second for 20 seconds is made into the femoral artery, immediately followed by a rapidly delivered bolus, typically 20 ml per second for 2 seconds. On completion of the injection, the low flow injection has reached the digital vessels and the high flow injection is localized in the distal aorta with all vessels between being opacified, whereby a single X-ray exposure may be taken from the aorta to the foot with the film positioned under the area of interest. The injection apparatus is relatively compact and permits both extension and retraction as well as rotation of the syringe assembly relative to the control cabinet. Suitable means are also provided for accommodating any misalignment between the syringe piston and ball screw shaft and also for absorbing the rotational forces acting on the ball screw shaft during axial movement thereof. A ground fault interrupter guards against current leakage to ground by removing the power from the motor and controls when the current leakage to ground exceeds a predetermined low level, for example, 0.5 milliamps.

Wootten et a1.

1 METHOD AND APPARATUS FOR INJECTING CONTRAST MEDIA INTO THE VASCULARSYSTEM {75] Inventors: John A. Wootten, South Euclid;

George S. Rives, Sheffield Lake, both of Ohio {73] Assignee: LearSiegler, Inc., Maple Heights,

Ohio

) [22] Filed: Mar. 12, 1973 [21] Appl. No.: 340,226

[52] -U.S. Cl. 128/2 R, 128/205 R, 128/215, 128/218 A, 128/D1G. 1,222/59, 222/76 [51] Int. Cl. A61b 5/02, A61m 5/20 [58] Field ofSearch... 128/218 A, 2 R, 2 A, D16. 1, 128/215, 236, 2.05 R; 222/59, 76,333

[56] References Cited UNITED STATES PATENTS 2,602,446 7/1952 Glass etal. 128/218 A 2,627,270 2/1953 Glass 128/218 A 3,631,847 1/1972 Hobbs128/218 A 3,156,236 11/1964 Williamson 128/2.05 R

3,335,724 8/1967 Gienapp 128/218 A 3,415,419 12/1968 Jewett et al 1.128/218 A 3,456,649 7/1969 .lewett 128/218 A 3,523,523 8/1970 Reich128/2.05 R

3,623,474 11/1971 Hellman 128/218 A 3,701,345 /1972 Heilman 128/218 A3,720,211 3/1973 Kyrias 128/218 A Primary Examiner-Aldrich F MedberyAttorney, Agent, or FirmDonnelly, Maky, Renner & Otto [451 May 28, 1974[57] ABSTRACT A method and apparatus by which fluid is delivered eithersequentially at two different rates or at one rate as desired. Suitablecontrols are provided for independently selecting such different flowrates and the duration of time of each flow rate, which may either bemanually or automatically delivered. During the injection cycle, a slowprolonged infusion, typically 2 ml per second for seconds is made intothe femoral artery, immediately followed by a rapidly delivered bolus,typically 20 ml per second for 2 seconds. On completion of theinjection, the low flow injection has reached the digital vessels andthe high flow injection is localized in the distal aorta with allvessels between being opacified, whereby a single X-ray exposure may betaken from the aorta to the foot with the film positioned under the areaof interest. The injection apparatus is relatively compact and permitsboth extension and retraction as well as rotation of the syringeassembly relative to the control cabinet. Suitable means are alsoprovided for accommodating any misalignment between the syringe pistonand ball screw shaft and also for absorbing the rotational forces actingon the ball screw shaft during axial movement thereof. A ground faultinterrupter guards against current leakage to ground by removing thepower from the motor and controls when the current leakage to groundexceeds a predetermined low level, for example, 0.5 milliamps.

26 Claims, 9 Drawing Figures 74 13 i 7 5 28 74 l l 12 58 32 so 29 51 5e10 4e as a 15 1e 34 l l I 50 11 49 YPATE'NTEDIAY 213 i914 SBEEIQBFS 1METHOD AND APPARATUS FOR INJECTING CONTRAST MEDIA INTO THE VASCULARSYSTEM BACKGROUND OF THE INVENTION This invention relates generally asindicated to an improved method and apparatus for injecting a contrastmedia into a persons vascular system.

It has become standard procedure to inject contrast media into thevascular system to study and obtain information about the arterial tree.Conventional practice has been to make multiple injections and take a series of X-rays where visualization of a substantial portion of thearterial tree is desired, particularly the entire arterial tree of alower extremity which is the most frequently involved site of anobstruction. The primary objection to this procedure is that it oftenrequires the patient to be subjected tomultiple injections, and alsoincreases the patients exposure to X-rays. The time required to carryout this procedure is also oftentimes lengthy, and it involves the useof relatively expensive equipment such as rapid film changers, movingtable, and special X-ray source.

Another objection to the procedure described above is that visualizationof the critical span is not always adequate, necessitating a repeat ofthe procedure at another time after the contrast media has disappearedfrom the system.

An improved arteriographic technique has been devised which providessimultaneous visualization of the entire arterial tree of a lowerextremity during a single injection without the use of a film changer.By this technique, a slow prolonged infusion, typically 2 ml per secondfor 20 seconds, is made into the femoral artery at the groin,immediately followed by a rapidly deliv ered bolus, typically 20 ml persecond for 2 seconds. On completion of the injection, the low flowinjection has reached the digital vessels and the final bolus is calizedin the distal aorta with all vessels between being opacified, whereby asingle X-ray exposure may be taken from the aorta to the root with thefilm positioned under the area of interest.

Using this latter technique, peripheral arteriography of the lowerextremities can be accomplished without multiple X-ray exposures, andwithout the need for such expensive equipment as rapid film changers,moving table top, or tedious flow measurement methods. A single punctureis made in the femoral artery, followed by low flow injection down theextremity, high flow retrograde into the aorta, and a single X-rayexposure from the aorta to the foot. This not only minimizes the timerequired for angiography of the extremities, but also substantiallycontributes to more complete opacification and renders exceptionallygood filling and visualization of the critical area.

This biphasic technique has previously been carried out on a limitedscale using hand injections. However, it has been found that the resultsobtained by such hand injections were not always consistent, and thefinal bolus could not always be delivered retrograde into the aorta.

SUMMARY OF THE INVENTION With the foregoing in mind, it is a principalobject of this invention to provide a method and apparatus for obtainingmuch more consistent results using the biphasic technique previouslydescribed.

Another object is to provide such a method and apparatus by which fluidmay be delivered from the injector sequentially at two different ratesor at one rate as desired.

Still another object is to provide such a method and apparatus whichpermit independent selection of both the flow rates and duration of timeof each.

Yet another object is to provide such a method and apparatus whichprovides for sequential injection of fluid at such different flow ratesand times utilizing either manual or automatic controls.

Still another object is to provide such an injection apparatus in whichmisalignment between the syringe piston and ball screw shaft isaccommodated and the rotational force acting of the ball screw shaft iseffectively absorbed during axial movement thereof.

Another object is to provide such an apparatus which is relativelysimple in construction and compact and provides for ready adjustment ofthe position of the syringe assembly both vertically and horizontally aswell as angularly relative to the control cabinet.

Another object is to provide such an injection apparatus with safetycontrols which remove the power from the syringe drive motor andcontrols when the current leakage to ground exceeds a predetermined lowlevel, for example, 0.5 milliamps.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described andparticularly pointed out in the claims, the following description andthe annexed drawings setting forth in detail a certain illustrativeembodiment of the invention, this being indicative, however, of but oneof the various ways in which the principles of the invention may beemployed.

BRIEF DESCRIPTION OF THE DRAWINGS In the annexed drawings:

FIG. 1 is a front elevation view of a preferred form of injectionapparatus constructed in accordance with this invention;

FIG. 2 is a fragmentary transverse section through the control cabinetand syringe assembly of the apparatus of FIG. 1, taken on the plane ofthe line 2-2 thereof;

FIG. 3 is a fragmentary isometric view on a somewhat reduced scale ofthe control cabinet and syringe assembly illustrating the range ofmovements of the syringe assembly relative to the control cabinet;

FIG. 4 is a top plan view of the syringe assembly of FIG. 2 as seen fromthe plane of the line 4-4 thereof;

FIG. 5 is a fragmentary enlarged longitudinal section through thesyringe assembly of FIG. 2, taken on the plane of the line 5-5;

FIG. 6 is an enlarged sectional view of the syringe piston seal of FIG.5;

FIG. 7 is a fragmentary transverse section through the syringe assemblyof FIG. 5 taken on the plane of the line '7-7;

FIG. 8 is a schematic diagram showing a control circuit for controllingthe operation of the injector apparatus of FIGS. 1 through 7; and

FIG. 9 is a schematic diagram showing a ground fault interrupter circuitfor providing protection against current leaks to ground.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in detail to thedrawings and initially to FIGS. 1 and 2 thereof, there is shown apreferred form of injection apparatus 1 in accordance with thisinvention including a syringe assembly 2 and control assembly 3 forcontrolling the operation thereof in a manner to be subsequentlydescribed. The syringe assembly 2 is desirably connected to the controlassembly by an elongated tube 4 which extends from one side of thesyringe assembly box 5 into the control cabinet 6 as clearly illustratedin FIG. 2.

Within the control cabinet 6 is a support 7 suitably attached to thebase plate 8 and having an opening therethrough in which the tube 4 isslidably received, permitting both longitudinal and rotational movementof the syringe assembly 2 relative to the control assembly 3. A pair ofspaced apart stop rods 9 paralleling the tube 4 limitsthe extent towhich the syringe assembly 2 may be rotated in either direction for alllongitudinal adjusted positions of the syringe assembly, there beingprovided a stop screw 10 on the distal end of the tube 4 which engagesone or the other of the stop rods 9 during rotation of the syringeassembly in opposite directions to limit such rotation and protect thewiring harness 11 leading from the control assembly to the syringeassembly through the hollow tube 4 against breakage. The stop screw 10also limits the maximum extent to which the syringe assembly 2 may beextended relative to the control assembly 3 by engagement with the fixedsupport 7. Preferably, the disposition of the stop rods 9, only one ofwhich is shown, is such that the syringe 12 of the syringe assembly 2may be tilted a maximum of +1 50 and l50 from the vertical asillustrated in FIG. 3, and the syringe assembly may also be extendedfrom 0 to approximately 18 inches from the control cabinet 6.

To secure the syringe assembly 2 in the desired longitudinal androtational adjusted positions, a lock knob 16 is provided on the controlcabinet 6. Tightening of the lock knob 16 causes the tube 4 to beclamped by a flexible collar 17 on the stationary support 7, the lockknob being connected to the collar 17 by a threaded rod 18. Furtheradjustments of the position of the syringe assembly 2 will be permittedupon loosening the lock knob 16 and subsequently retightening the sameafter the syringe assembly has been moved to the desired adjustedposition.

For ease of portability of the injector apparatus 1, the controlassembly 3 may be mounted on a mobile support stand 19 with a triangularbase 20 on which are mounted swivel casters 21 as shown in FIG. 1 topermit the unit to be wheeled about. Each caster 21 desirably includes aseparate lock 22 which when turned in one direction locks the casteragainst rotation and when turned in the opposite direction unlocks thecaster.

Adjacent the upper end of the stand column 19 may be provided a columnadjustment handle 23 for raising and lowering of the control assembly 3and syringe assembly 2 attached thereto. The height of the injector 1 isdesirably adjustable from approximately 38 to 57 inches by rotation ofthe column adjustment handle 23 in opposite directions, and a columnlock nut 24 is desirably provided for locking the control assembly andsyringe assembly in the desired vertical adjusted position.

As best seen in FIGS. 5 and 7, the syringe assembly 2 includes a mainsupport housing 28 to which is bolted a syringe housing 29 for receiptof the barrel 30 of the syringe 12. The syringe barrel 30 has a radialoutwardly projecting flange 31 intermediate the ends of the barrel foraccurately locating and clamping the barrel within the syringe housing29. A syringe hold-on nut 32 having threaded engagement with the OD ofthe syringe housing 29 releasably retains the syringe barrel 30 withinthe syringe housing 29, and suitable plastic insulators 33 interposedbetween the hold-on nut 32 and syringe barrel 30 and syringebarrel andsyringe housing 29 electrically isolate the syringe barrel from thevarious other parts of the apparatus.

Axially extending into the syringe barrel 30 is a ball screw shaft 34which has a push-pull screw 35 threaded into the forward end thereof tofacilitate positive attachment of a syringe piston 36 to the ball screwshaft. The syringe piston 36 is shown screwed onto a screw lock-on nut37 which has a polygonal shaped recess 38 therein of a shapecorresponding to but slightly larger than the head 39 of the push-pullscrew 35 for receipt of such head within the recess. The enlarged recess38 within the screw lock-on nut 37 provides a radial clearance with thepush-pull screw 35 to accommodate any misalignment between the syringepiston 36 and ball screw shaft 34 while still permitting positivepushing and pulling of the syringe piston within the syringe barrel 30during axial inward and outward movement of the ball screw shaft. Makingthe nut recess 38 and screw head 39 of a corresponding polygonal shapealso permits unscrewing of the syringe piston assembly 36 from the ballscrew shaft 34 for sterilization of the syringe piston assembly asdescribed hereafter.

To maintain a fluid-tight sliding seal between the syringe piston 35 andwall 40 of the syringe barrel v30, the syringe piston may be providedwith an annular external groove 41 containing a Teflon slipper seal 42,with an O-ring 43 between the slipper seal 42 and bottom of the groove41 which acts as a spring for maintaining the slipper seal in sealingcontact with the syringe barrel wall as clearly shown in FIG. 6.

Threadedly received in the outer end of the syringe barrel 30 is asee-through syringe cap 45 having a central longitudinal passage 46therethrough permitting expulsion of the fluid from the syringe duringlongitudinal movement of the syringe piston 36 within the syringe barrel30 in the direction of the syringe cap. An O-ring 47 is confined betweenthe syringe cap 46 and an internal shoulder 48 on the syringe barrel toprovide a fluid seal therebetween.

The inner end of the ball screw shaft 34 is received in a longitudinallyextending generally channel-shape raceway 49 in the main housing 28 andis retained against rotation by a pair of ball bearing assemblies 50disposed on opposite sides of the screw shaft and connected thereto by adowel pin 51 extending through the center of the ball screw shaft andball bearings. Such ball bearings 50 absorb any rotational forcesapplied to the ball screw shaft 34 and support the inner end of the ballscrew shaft for axial movement in either direction along the raceway 49.

Axial movement of the ball screw shaft 34 is obtained by rotation of aball screw nut 55 having threaded engagement with the ball screw shaftand driven by a gear 56 suitably journaled within a gear box 57 betweenthe main support housing 28 and the syringe housing 29 which provides acover for the gear box.

Rotation of the main gear 56 may be accurately controlled by an electricmotor 58, preferably a DC motor, with suitable motor mounts 59 beingprovided for direct attachment of the motor 58 to the main supporthousing 28. A suitable clutch mechanism 60 is desirably used to transmitpower from the drive motor 58 to the main gear 56 to protect the motoragainst overload and the various other parts of the syringe againstdamage in the event that the syringe piston 36 bottoms out with themotor still running or limits the pressure build up within the syringebarrel 30 due to fluid blockage or other reason.

As seen in FIG. 5, the clutch mechanism 60 may comprise a drive pinion61 with driven clutch face 62 freely rotatable on the outer end of themotor shaft 63 and retained in place by a thrust washer 64 and screw 65attached to the free end of the motor shaft. A clutch disc 66 keyed tothe motor shaft 63 for rotation therewith is maintained in drivingengagement with the driven clutch face 62 by a clutch spring 67 as longas the force required to transmit axial motion to the ball screw shaft34 and syringe piston 36 does not exceed a predetermined level. Theclutch spring 67 is confined between the clutch disc 66 and a clutchspring retainer 68 retained on the motor shaft by a snap ring 69 or thelike. The axial location of the syringe piston 36 within the syringebarrel 30 is indicated by a syringe piston position indicating rod 70attached to the inner end of the ball screw shaft 34. The positionindicating rod 70 may be secured in place by a set screw 71 threadedinto a recess in the inner end of the ball screw shaft. The sheet metalcover 5 which surrounds the syringe assembly 2 has a longitudinallyextending slot 72 in the top panel thereof for receipt of the upper endof the position indicator rod making it visible to the operator. Apiston position indicator sight glass 73 is shown covering thelongitudinally extending slot 72 and retained in place by a pair ofmounting brackets 74 suitably fastened to the cover 5 at opposite endsof the slot. As clearly shown in FIGS. 3 and 4, the sight glass 73 mayhave suitable indicia thereon and the sides of the longitudinal slot mayhave a calibrated scale to indicate the actual volume of contrast agentin the syringe 12 from to 120cc indicated by the position of theindicator rod 70 with respect to the calibrated scale. A pair of limitswitches 75, 76 mounted in spaced apart relation on the main supporthousing 28 adjacent the raceway 49 are engaged by the position indicatorrod 70 when the syringe piston 36 reaches either end of its stroke toshut off the motor 58.

The main support housing 28, in addition to providing a gear box 57 andraceway 49 for the ball screw shaft 34 and support for the syringe drivemotor 58 and limit switches 75, 76 therefor, also contains a recess 78for receipt of one end of the tube 4 which connects the syringe assembly2 to the control assembly 3. As clearly shown in FIG. 7, the connectingtube 4 is retained in place within the recess 78 in the main supporthousing 28 by a bolt 79. A mounting ring 80 surrounding the connectingtube 4 is attached to the main support housing 28 by suitable fastenersto secure the sheet metal cover 5 to the main support housing. A weight81 is also suitably attached to the main support housing 28 or motor 58to locate the center of gravity of the syringe assembly 2 closelyadjacent the axis of the tube 4 to facilitate tilting of the syringeassembly to any desired position as previously described.

Surrounding the syringe barrel 30 is a thermostatically controlledsyringe blanket 85 for heating the contrast media from room temperatureto 96 to 100 F and maintaining such temperature within twenty minutesafter filling the syringe and turning on the main power. Both theblanket and thermostat 85 are desirably molded in rubber and insulatedfrom the syringe 12.

The syringe is also electrically insulated from the syringe housing 29by the plastic spacers 33'previously described, and the injectorapparatus 1 has a ground clip 86 which is connected to the ground pin onthe power cord 87. A ground fault interrupter circuit to be laterdescribed is also desirably provided to remove the power from the motorand controls and provide a signal or alarm whenever there is a currentleakage to ground exceeding 0.5 milliamps.

Both the main support housing 28 and syringe housing 29 are desirablymade of aluminum for reduced weight, whereas the syringe barrel 30 isdesirably made of non-corrosive high strength material such as stainlesssteel. The see-through syringe cap 45 is desirably made of polycarbonateand the syringe piston 36 of delrin, both autoclavable to 250 F forsterilization.

The various parts of the syringe 12 are disassembled to permitsterilization thereof. Before disassembling the syringe, the syringepiston 36 is desirably moved to the Occ position as indicated by thevolume indicator rod 70. Then the large nut 32 holding the syringe tothe syringe housing 29 may be removed to permit the seethrough syringecap 45 and syringe barrel 30 to be pulled out of the syringe housing.Next the see-through syringe cap 45 may be unscrewed from the syringebarrel 30 and the O-ring 47 removed, after which the syringe pistonassembly 36 may be unscrewed from the ball screw shaft 34, leaving thecap seal 42, 43 on the syringe piston.

After the various syringe parts have been sterilized, the syringe piston36 is screwed back onto the ball screw shaft 34 and the syringe barrel30 is pushed into place and retained therein by screwing the large nut32 back on to firmly clamp the radial flange 31 on the syringe barrel inplace adjacent the end of the syringe housing 29.

Next the syringe piston 36 is retracted until the indicator readingcorresponds to the desired volume of contrast media with which thesyringe is to be filled. Then the lock knob 16 on the control cabinet 6is loosened to permit the syringe assembly 2 to be rotated until thesyringe 12 is pointing vertically upward so that the contrast media maybe poured directly into the syringe barrel, keeping the fluid levelbelow the O-ring groove 48.

Before filling the syringe barrel, the O-ring 47 is inserted into theO-ring groove 48 and afterwards the see-through cap 45 is screwed intothe barrel until it bottoms against the O-ring. Next one end of acatheter may be connected to the luer loc fitting on the seethroughsyringe cap 45 and the other end inserted into an empty contrast mediabottle to permit the syringe piston 36 to be moved slightly forward toexpress any trapped air from the syringe or catheter. Finally, the lockknob 16 is loosened and the syringe assembly 2 rotated until the tip ofthe syringe 12 is pointing down from the horizontal at a maximum anglefrom the horizontal of approximately 60.

Suitable controls are provided on the control panel 88 which permitselection of two different flow rates for two different periods of time.Separate control knobs are provided for selecting each rate of flow incubic centimeters per second and the time of each flow rate in seconds.The first slow inject flow control knob 89 permits a selection of a flowrate of anywhere from 0.3 to cc per second for a period of time anywherefrom off to 25 seconds as determined by the setting of a second controlknob or dial 90. The first rapid inject flow control knob 91 permits theselection of a flow control rate of anywhere from 5 to 40cc per secondfor a period of time anywhere from off to 6 seconds as determined bystill another control knob 92. The product of the flow rate and time foreach of the slow and rapid inject phases will determine the volume offluid injected during each phase of injection.

An additional control knob 93 may also be provided on the control panel88 for selecting a delay period, for example, from 0 to 2 seconds aftercompletion of the entire injection phase for triggering the X-rayexposure. An X-ray cable connector 94 is shown for connecting thecontrol box to an X-ray machine.

Also provided on the control panel 88 are a lighted on-off power switch95 which includes a amp circuit breaker, a manual loading and unloadingswitch 96, and a lighted armed/unarmed selector switch 97. The manualloading or unloading switch 96 is used to fill or empty the syringe 12when the armed/unarmed switch 97 is in the unarmed position. When thearmed/unarmed switch 97 is in the armed position, the unit may beoperated by a remote control or hand trigger switch 98 to injectcontrast media into a patient either manually or automatically asdescribed hereafter.

A lighted safe/unsafe ground fault interrupter switch 99 and associatedcircuit detects current leaks to ground above 0.5 milliamps, andautomatically moves from the safe to unsafe position when the powerswitch 95 is on to remove power from the control and syringe assemblies.A ground fault interrupter push to test switch 100 is also provided forchecking the operation of the ground fault interrupter circuit. Correctoperation of the ground fault interrupter circuit is indicated during atest when the unsafe light comes on and an audible alarm sounds. To turnthe unsafe light off and stop the audible alarm after completion of atest merely requires pushing the safe/unsafe switch 99 to the safeposition.

With the armed/unarmed switch 97 in the armed position, depressing andreleasing the automatic position on the hand trigger switch 98 willcause the injector apparatus l to automatically sequentially inject thetwo different flow rates selected on the flow and rapid inject flow rateand time control dials 89, 90 and 91, 92, respectively. However, theinjection may be stopped at any time during the automatic injectionphase by depressing and releasing the manual position on the handtrigger switch 98. Alternatively, the entire injection phase will remainunder the direct control of the operator by pressing the manual positionon the hand trigger switch. Releasing the manual position on the handtrigger switch at any time will immediately'stop the injection.

Having thus described the various parts of the injector apparatus, abrief description of its operation will be set forth.

OPERATION To operate the injector apparatus 1, the control assembly 3should first be raised to the desired height by loosening the stand lockknob 24 and rotating the stand adjustment handle 23 to raise or lowerthe control and syringe assemblies 3, 2 to the desired height, afterwhich the lock knob may be tightened to hold such assemblies in thedesired vertical adjusted position. The power cord 87 should then beplugged into a suitable power source and the lighted main power switchturned on, followed by a testing of the ground fault interrupter circuitas previously described. If the ground fault interrupter circuit checksout properly, the safe- Iunsafe switch 99 should be pushed to the safeposition to turn off the unsafe light and stop the audible alarm whichshould have gone on when the test switch was depressed to indicate acorrect operation of the ground fault interrupter circuit.

The load/unload switch 96 should then be held in the unload positionuntil the syringe piston 36 is at the Doc position to facilitatedisassembly and sterilization of the syringe as previously described.After sterilization, the syringe piston 36 and syringe barrel 30 shouldbe reassembled and with the armed/unarmed switch 97 in the unarmedposition the load/unload switch 96 moved to the unload position toretract the syringe piston to the desired volume of contrast media asshown on the indicator rod 70. Then the cabinet lock knob 16 should beloosened to permit the syringe assembly 2 to be rotated until thesyringe 12 extends vertically upward and with O-ring 47 in place thecontrast media may be poured into the syringe barrel, keeping the fluidlevel below the O-ring groove 48. After filling, the syringe cap 45should be threaded into position in the upper end of the syringe barrel30.

Next one end of a catheter may be connected to the syringe cap 45 andthe other end inserted into an empty contrast media bottle so that theunload switch 96 may be depressed to express any trapped air in thesyringe or catheter.

Thereafter the cabinet lock knob 16 should be loosened to permit thesyringe 12 to be rotated until its tip is pointing down from thehorizontal. The syringe assembly 2 may also be extended horizontallyfrom the control assembly 3 to the extent desired, followed by atightening of the cabinet lock knob to lock the syringe in the desiredposition.

Next both the slow inject control knobs 89 and 90 and rapid injectcontrol knobs 91 and 92 should be set to the desired flow rates andperiods of time for each flow rate, and the X-ray delay control knob 93should also be set to the desired time delay for the X-ray exposureafter completion of the entire injection phase. The X-ray cable 94should also be properly connected both to the control assembly 3 and tothe X-ray machine.

The injector apparatus 1 is now ready to be used to inject contrastmedia or other fluid into the patient after the catheter needle has beenproperly inserted. The injection phase is under the control of the handtrigger switch 98 as soon as the armed/unarmed unarmed selector switch97 is moved to the armed position, whereby movement of the hand triggerswitch either to the automatic or manual positions will cause thecontrast media to be injected into the patient. When the hand triggerswitch 98 is depressed in the automatic direction, the switch may bereleased and the injector apparatus will still continue to inject thefluid into the patient in accordance with the programmed flow rates andtimes. However, such procedure may be interrupted at any time bydepressing the hand trigger switch 98 in the manual direction andreleasing it. Moving the hand trigger switch 98 in the manual directionrequires the operator to continue to press the switch during manualinjection since releasing the trigger switch after pushing it in themanual direction will immediately stop the injection.

On completion of the injection, the X-ray machine will be automaticallytriggered after a time delay of from to 2 seconds as determined by thesetting of the X-ray delay control knob 93. By then the earliestdelivered contrast media has reached the digital vessels, while thefinal bolus is in the distal aorta with all vessels in betweenopacified. The X-ray source is desirably elevated maximally, preferablyto six feet, and the X-ray film is positioned along the entire lengthunder study, with appropriate filters. A single, long film holder ispreferred, but multiple, overlapping film holders may also be used.

THE CONTROL CIRCUIT FIG. 8 is a schematic diagram of the primary controlcircuit 105 for controlling the operation of the injection apparatus 1previously described. Included in the circuit is the circuit breaker andon-off switch 95 which must be depressed to energize the circuit. Alight 106 signals that the power is on, and the circuit breaker 107protects the circuit against an overload. The power to the circuitpasses through a differential transformer 108 which produces a signal inthe transformer core 109 whenever the current through the two coils 110,111 is different, as when there is a current leakage to ground. Thissignal is picked up by the output coil 112 of a ground fault interrupteramplifier circuit 115, schematically illustrated in FIG. 9, whichamplifies the signal to energize a relay R1, causing the safe/unsafeswitch 99 to open thereby removing the power from the motor andcontrols. When this occurs, a second relay R2 is deenergized causing theassociated switch S2 to close which lights the unsafe light 116 andsounds a buzzer or alarm 117. Such a ground fault interrupter circuit115 is desirably sufficiently sensitive to detect current leaks toground above 0.5 milliamps.

The ground fault interrupter test switch 100 is connected to a suitableresistor 118 for simulating a current leakage when the test switch 100is depressed to check the operation of the fault interrupter circuit115. Correct operation of the ground fault interrupter circuit 115 isindicated when, upon pushing the test switch 100, the unsafe light 116goes on and the buzzer or alarm 117 sounds.

To reactivate the primary control circuit 105 upon release of the testswitch 100, the operator need only depress the ground fault interrupterswitch 99 to energize the relay R2 which opens the portion of thecircuit including the unsafe light 116 and buzzer 117 causing them to beturned off.

When the primary control circuit is energized, power is supplied to theheater 85 surrounding the syringe barrel 30 which is controlled by thethermostat to heat the contrast media from room temperature toapproximately 96 to 100 F and maintain the contrast media at thattemperature.

The armed/unarmed selector switch 97 may be moved between the unarmedposition shown in FIG. 6 in which operation of the syringe drive motor58 may be manually controlled by the loading and unloading switch 96 andthe armed position in which such motor may be controlled by the handtrigger switch 98. When the armed/unarmed selector switch 97 is in theunarmed position shown, the hand trigger switch 98 is taken out of theprimary control circuit and the load- /unload switch 96 is in thecircuit permitting manual operation of the syringe drive motor 58 inopposite directions by moving the load/unload switch to the load andunload positions for respectively filling or emptying the syringe 12.,

When the load/unload switch 96 is moved to the unload position, therelay R3 is activated which closes the associated motor contacts C3causing the motor to extend the syringe piston 36 for unloading thesyringe. Movement of the load/unload switch 96 to the load positionactivates another relay R4 which closes its respective motor contacts C4causing the direction of rotation of the motor 58 to be reversed toretract the syringe piston 36 for loading the syringe.

The speed of the drive motor 58 when under the control of theload/unload switch 96 is desirably greater during operation in theloading direction than in the unloading direction and is controlled bythe amount of resistance in the SCR firing circuit. A field relay FR inthe load/unload circuit activates its associated contacts CF 1 when theload/unload switch is moved either to the load or unload positions tosupply current to the motor field circuit. A manual relay MR switchesbetween the two motor speeds for loading and unloading the syringe. Whenthe switch 96 is moved to the unload position, the manual relay MR isenergized, causing the associated contact CMl to be opened, whereby thespeed of the motor 58 is controlled by the resistor for unloading thesyringe, whereas when the switch 96 is moved to the load position, themanual relay MR is not energized, causing the associated contact CMl tobe closed, whereby the speed of the motor is controlled by the resistor126 for loading the syringe.

Since the speed of the syringe piston 36 need not be adjustable duringthe manual load and unload modes, fixed resistors 125, 126 may be usedto control the speed of the motor during such modes. Preferably, suchresistors 125, 126 are selected so that when the load- /unload switch 96is moved to the load position the syringe piston will be retracted tofill the syringe at a rate of approximately 6cc per second and when theswitch 96 is moved to the unload position the syringe will be extendedto empty the syringe at a rate of approximately l.3cc per second.Separate limit switches 75 and 76 are provided in the unload and loadcircuits, respectively, for opening their respective contacts when thesyringe piston 36 reaches the respective ends of its stroke.

Movement of the armed/unarmed switch 97 to the armed position removesthe load/unload switch 96 from the primary control circuit and readiesthe circuit for the injection phase through actuation of the handtrigger or remote control switch 98. The position of the armed/unarmedswitch 97 may readily be indicated by providing indicator lights 127 and128 in the respective armed and unarmed circuits. Current iscontinuously supplied to the motor field windings when the injectorapparatus is in the armed mode to avoid any time lag in building up themagnetic field during the normal injection phase, whereas during theunarmed mode, the motor field is only turned on when the field relay FRis energized by movement of the load/unload switch 96 to either of theload or unload positions.

During the armed mode, the two manual motor speed resistors 125 and 126are removed from the primary control circuit and the hand trigger orremote control switch 98 is operative to control the movement of thesyringe piston 36 in the injection direction only. The hand triggerswitch 98 desirably includes both an automatic position 130 and anoff/manual position 131. When the switch 98 is moved to the automaticposition 130, the relay R6 is activated causing the associated contactsC6, C6 to close, and such contacts C6, C6 will remain closed even thoughthe hand trigger switch 98 is released to cause automatic sequentialinjection of the fluid as determined by the settings of the slow andrapid inject control knobs 89, 90 and 91, 92. However, the injection maybe stopped at any time during the automatic injection phase by movingthe switch 98 to the off/manual position 131 and releasing the switch.When the switch 98 is moved to the off/manual position, it activates thejog relay R7 which opens the contact C7 in the automatic controlcircuit, deenergizing the relay R6 and opening the associated contactsC6, C6 whereby when the switch 98 is then released, the injector motorwill stop. Movement of the switch 98 -to the off or manual position alsocauses the jog relay R7 to close another contact C7 for manual operationof the injector during the armed mode. Releasing the switch 98 from themanual position will automatically stop the injection.

When the hand trigger switch 98 is moved either to the automatic ormanual positions 130 or 131, a relay LR is energized which closes itsassociated contact CL for controlling the speed of the drive motorduring slow injection as determined by the setting of the potentiometercontrol knob 89. A time delay relay T1 is energized at the end of itstiming cycle as set by the slow inject time potentiometer control knob90 to open the contact CTl associated with the slow inject potentiometercontrol knob 89 and close the contact CTl associated with the rapidinject potentiometer control knob 91 for automatically switching fromslow inject to rapid inject at the end of the slow inject time. The timedelay relay Tl also closes a switch CTl for actuating a second timedelay relay T2 at the end of its timing as set by the rapid inject timecontrol knob 92. When the time delay relay T2 is energized, it closesthe contact CTZ for activating the X-ray time delay relay T3 after adelay of from to 2 seconds as set on the X-ray delay control knob 93. Ifthe syringe piston 36 reaches the end of its stroke during the armedmode before the relay T3 is activated, the limit switch [32 will betripped, stopping the drive motor 58 and activating the X-ray time delayrelay T3 as previously described. The relay contacts C3, C4 on the motorprovide dynamic braking when both contacts are closed by creating amagnetic field which brakes the motor, as well known in the art.

Although a single drive motor 58 is shown, it will be apparent that twodifferent speed drive motors may be used for the slow and rapid modes ofinjection, respectively. Alternatively, two different gear boxes may beused in conjunction with a single drive motor, with clutches to switchthe motor from one gear box to the other for slow and rapid injection.

Conventional feedback controls such as disclosed in U.S. Pat. Nos.3,623,474 and 3,631,847 may also be provided for measuring andcontrolling the speed of the syringe piston throughout the period ofinjection to obtain predictable, controlled flow rates under varyingconditions. Alternatively, various other control systems may be used toaccomplish substantially the same results, including, for example, anoptical feedback to monitor the motor speed; a highly regulated DC powersupply wherein the voltage supplied to the motor is monitored and fedback to control the power supply; or an open loop frequency controlsystem utilizing an RC circuit with a variable resistance and aunijunction transistor to create a variable frequency pulse to operatethe motor.

From the foregoing, it will now be apparent that the method andapparatus of the present invention minimize the time required forangiography of the extremities, reduce the amount of apparatus, andsubstantially contribute to more complete opacification andvisualization. Such a method and apparatus also make X-ray exposureminimal with fewer injections and smaller volumes of contrast media. Theinjector apparatus may also be used for other arteriographic proceduresas well, including conventional angiography, by using either the slowinject or rapid inject modes separately. The controls for the mode notused are simply set at 60.,

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. lnjection apparatus for injecting a fluid into the vascular system ofa mammal comprising a syringe assembly including a syringe barrelcontaining a piston, means mounting said piston for axial movementwithin said syringe barrel for expelling said fluid therefrom, andcontrol means for controlling the rate of speed of advance movement ofsaid piston within said syringe barrel, said control means comprisingmeans for independently preselecting more than one rate of speed ofadvance movement of said piston within said syringe barrel and theperiods of times of duration of each advancement prior to suchadvancement, and means for sequentially advancing said piston at suchpreselected rates of speed for such preselected periods of time duringsuch advancement of said piston.

2. The apparatus of claim 1 wherein said control means further comprisesmeans for selectively stopping and restarting said piston at any timeduring such advancement.

3. The apparatus of claim 1 wherein said control means further comprisesswitch means including an automatic position which when depressed andreleased causes said piston to automatically sequentially advance atsuch preselected rates of speed for such preselected periods of time,and an olT/manual position which when depressed and released stops suchautomatic advancement of said piston but continues such advancement aslong as such off/manual position is depressed.

13 4. The apparatus of claim 1 wherein said control means furthercomprises means for preselecting a time delay for actuation of an X-raymachine upon completion of such sequential advancement of said piston.

5. The apparatus of claim 4 wherein said control means further compriseslimit switch means for activating said time delay for such X-ray machinein the event that said piston reaches the end of its stroke before thepreselected time.

6. The apparatus of claim 1 wherein said control means further comprisesan electric motor for driving said piston, and means for varying thespeed of said electric motor to vary the speed of advancement of saidpiston in accordance with the preselected settings of said controlmeans.

7. The apparatus of claim 6 further comprising clutch means fortransmitting power from said motor to said piston to protect againstdamage if said piston bottoms out and limit pressure developed.

8. The apparatus of claim 6 wherein said control means further comprisesmeans for causing said motor to rotate in opposite directions to retractand extend said piston for respectively filling and emptying saidsyringe barrel.

9. The apparatus of claim 8 wherein said control means further comprisesmeans for causing said motor to rotate at a slower speed duringextension of said piston for emptying said syringe barrel than duringretraction of said piston for filling said syringe barrel.

10. The apparatus of claim 8 further comprising limit switches forstopping said motor when said piston reaches either end of its stroke.

11. The apparatus of claim 6 further comprising a ground faultinterrupter circuit associated with said control means for detectingcurrent leaks to ground and removing the power from said control means.

12. The apparatus of claim 11 wherein said control means furthercomprises means for testing said ground fault interrupter circuit tocheck its operation.

13. The apparatus of claim 1 further comprising means for moving saidpiston at a faster rate for filling said syringe barrel than foremptying said syringe barrel.

14. The apparatus of claim I further comprising means for checking saidsyringe assembly for current leaks to ground prior to filling saidsyringe assembly with the desired quantity of fluid.

15. The apparatus of claim 1 further comprising a syringe cap andassociated seal on the outer end of said syringe barrel.

16. Injection apparatus for injecting a fluid into the vascular systemof a mammal comprising a syringe assembly including a syringe barrelcontaining a piston, means mounting said piston for axial movementwithin said syringe barrel for expelling said fluid therefrom, andcontrol means for controlling the rate of speed of advance movement ofsaid piston within said syringe barrel, said control means comprisingmeans for independently preselecting more than one rate of speed ofadvance movement of said piston within said syringe barrel and volumesof each advancement prior to such advancement, and means forsequentially advancing said piston at such preselected rates of speedfor such preselected volumes during such advancement of said piston.

17. Injection apparatus for injecting a fluid into the vascular systemof a mammal comprising a syringe assembly including a syringe barrelcontaining a piston, and means mounting said piston for axial movementwithin said syringe barrel for expelling fluid therefrom, saidlast-mentioned means comprising a ball screw shaft connected to saidpiston, means mounting said ball screw shaft for axial movement but notrotational movement, a ball nut threadedly engaging said ball screwshaft, whereby rotation of said nut causes axial movement of saidpiston, and means for rotating said nut, said means mounting said ballscrew shaft for axial movement but not rotational movement comprising amain support housing containing a longitudinally extending raceway forsaid ball screw shaft, said raceway being of generally channel shape,and a pair of ball bearing assemblies disposed on opposite sides of saidball screw shaft and connected thereto by a dowel pin extending throughthe center of said ball screw shaft and ball bearing assemblies, saidball bearing assemblies engaging said raceway to support said ball screwshaft for axial movement along said raceway and ab.- sorb any rotationalforces acting on said ball screw shaft during such axial movementthereof.

18. The apparatus of claim 17 further comprising means providing apositive push-pull connection between said piston and ball screw shaftwhile accommodating any axial misalignment therebetween.

19. The apparatus of claim 18 wherein said lastmentioned means comprisesa nut onto which said piston is threaded, said nut having a polygonalshaped recess therein, a push-pull screw attached to the outer end ofsaid ball screw shaft, said screw having a head of a shape correspondingto the polygonal recess in said nut but slightly smaller than saidrecess for receipt therein with some radial clearance to accommodate anysuch misalignment between said piston and ball screw shaft while stillpermitting positive pushing and pulling of said piston during axialinward and outward movement of said ball screw shaft.

20. Injection apparatus for injecting a fluid into the vascular systemof a mammal comprising a syringe assembly including a syringe barrelcontaining a piston, means mounting said piston for axial movementwithin said syringe barrel for expelling fluid therefrom, and a mainsupport housing for said syringe assembly, said main support housinghaving an elongated tube projecting therefrom, and a control assemblyfor controlling the operation of said syringe assembly, said elongatedtube extending into said control assembly, said control assemblyincluding a support having an opening therethrough in which said tube isslidably received to permit both longitudinal and rotational movement ofsaid syringe assembly relative to said control assembly, a pair ofspaced apart stop rods mounted within said control assembly parallelingsaid tube adjacent opposite sides thereof, a stop screw on the distalend of said tube engageable with said stop rods to limit the rotation ofsaid tube in opposite directions for all longitudinal adjusted positionsof said syringe assembly relative to said control assembly, and meansfor clamping said syringe assembly in the desired longitudinal androtational adjusted positions.

21. The apparatus of claim 20 wherein said means for clamping saidsyringe assembly in the desired longitudinal and rotational adjustedpositions comprises a lock knob on said control assembly, a flexiblecollar surrounding said tube, and a rod extending from said lock knoband having threaded engagement with said collar for loosening andtightening said collar on said tube by rotation of said lock nut inopposite directions.

22. The apparatus of claim further comprising a weight attached to saidsyringe assembly for locating the center of gravity of said syringeassembly closely adjacent the axis of rotation of said tube tofacilitate rotation of the syringe assembly to any desired adjustedposition.

23. The apparatus of claim 20 further comprising a support stand forsaid control assembly, and means mounting said control assembly on saidsupport stand for vertical movement to provide for adjustment of thevertical height of the control assembly and syringe assembly connectedthereto.

24. The apparatus of claim 20 wherein said means for moving said pistonaxially within said syringe barrel includes an electric motor fordriving said piston, and clutch means for transmitting power from saidmotor to said piston to protect against damage if said piston bottomsout and limit pressure developed.

25. The apparatus of claim 24 further comprising a syringe housingsurrounding said syringe barrel, means for releasably mounting saidsyringe barrel within said syringe housing, and means for electricallyisolating said syringe barrel from said syringe housing.

26. The apparatus of claim 25 wherein said syringe housing includes agear box containing drive mechanism for driving said piston by saidmotor, said syringe housing being attached to said main housing toprovide a cover for said gear box.

1. Injection apparatus for injecting a fluid into the vascular system ofa mammal comprising a syringe assembly including a syringe barrelcontaining a piston, means mounting said piston for axial movementwithin said syringe barrel for expelling said fluid therefrom, andcontrol means for controlling the rate of speed of advance movement ofsaid piston within said syringe barrel, said control means comprisingmeans for independently preselecting more than one rate of speed ofadvance movement of said piston within said syringe barrel and theperiods of times of duration of each advancement prior to suchadvancement, and means for sequentially advancing said piston at suchpreselected rates of speed for such preselected periods of time duringsuch advancement of said piston.
 2. The apparatus of claim 1 whereinsaid control means further comprises means for selectively stopping andrestarting said piston at any time during such advancement.
 3. Theapparatus of claim 1 wherein said control means further comprises switchmeans including an automatic position which when depressed and releasedcauses said piston to automatically sequentially advance at suchpreselected rates of speed for such preselected periods of time, and anoff/manual position which when depressed and released stops suchautomatic advancement of said piston but continues such advancement aslong as such off/manual position is depressed.
 4. The apparatus of claim1 wherein said control means further comprises means for preselecting atime delay for actuation of an X-ray machine upon completion of suchsequential advancement of said piston.
 5. The apparatus of claim 4wherein said control means further comprises limit switch means foractivating said time delay for such X-ray machine in the event that saidpiston reaches the end of its stroke before the preselected time.
 6. Theapparatus of claim 1 wherein said control means further comprises anelectric motor for driving said piston, and means for varying the speedof said electric motor to vary the speed of advancement of said pistonin accordance with the preselected settings of said control means. 7.The apparatus of claim 6 further comprising clutch means fortransmitting power from said motor to said piston to protect againstdamage if said piston bottoms out and limit pressure developed.
 8. Theapparatus of claim 6 wherein said control means further comprises meansfor causing said motor to rotate in opposite directions to retract andextend said piston for respectively filling and emptying said syringebarrel.
 9. The apparatus of claim 8 wherein said control means furthercomprises means for causing said motor to rotate at a slower speedduring extension of said piston for emptying said syringe barrel thanduring retraction of said piston for filling said syringe barrel. 10.The apparatus of claim 8 further comprising limit switches for stoppingsaid motor when said piston reaches either end of its stroke.
 11. Theapparatus of claim 6 further comprising a ground fault interruptercircuit associated with said control means for detecting current leaksto ground and removing the power from said control means.
 12. Theapparatus of claim 11 wherein said control means further comprises meansfor testing said ground fault interrupter circuit to check itsoperation.
 13. The apparatus of claim 1 further comprising means formoving said piston at a faster rate for filling said syringe barrel thanfor emptying said syringe barrel.
 14. The apparatus of claim 1 furthercomprising means for checking said syringe assembly for current leaks toground prior to filling said syringe assembly with the desired quantityof fluid.
 15. The apparatus of claim 1 further comprising a syringe capand associated seal on the outer end of said syringe barrel. 16.Injection apparatus for injecting a fluid into the vascular system of amammal comprising a syringe assembly including a syringe barrelcontaining a piston, means mounting said piston for axial movementwithin said syringe barrel for expelling said fluid therefrom, andcontrol means for controlling the rate of speed of advance movement ofsaid piston within said syringe barrel, said control means comprisingmeans for independently preselecting more than one rate of speed ofadvance movement of said piston within said syringe barrel and volumesof each advancement prior to such advancement, and means forsequentially advancing said piston at such preselected rates of speedfor such preselected volumes during such advancement of said piston. 17.Injection apparatus for injecting a fluid into the vascular system of amammal comprising a syringe assembly including a syringe barrelcontaining a piston, and means mounting said piston for axial movementwithin said syringe barrel for expelling fluid therefrom, saidlast-mentioned means comprising a ball screw shaft connected to saidpiston, means mounting said ball screw shaft for axial movement but notrotational movement, a ball nut threadedly engaging said ball screwshaft, whereby rotation of said nut causes axial movement of saidpiston, and means for rotating said nut, said means mounting said ballscrew shaft for axial movement but not rotational movement comprising amain support housing containing a longitudinally extending raceway forsaid ball screw shaft, said raceway being of generally channel shape,and a pair of ball bearing assemblies disposed on opposite sides of saidball screw shaft and connected thereto by a dowel pin extending throughthe center of said ball screw shaft and ball bearing assemblies, saidball bearing assemblies engaging said raceway to support said ball screwshaft for axial movement along said raceway and absorb any rotationalforces acting on said ball screw shaft during such axial movementthereof.
 18. The apparatus of claim 17 further comprising meansproviding a positive push-pull connection between said piston and ballscrew shaft while accommodating any axial misalignment therebetween. 19.The apparatus of claim 18 wherein said last-mentioned means comprises anut onto which said piston is threaded, said nut having a polygonalshaped recess therein, a push-pull screw attached to the outer end ofsaid ball screw shaft, said screw having a head of a shape correspondingto the polygonal recess in said nut but slightly smaller than saidrecess for receipt therein with some radial clearance to accommodate anysuch misalignment between said piston and ball screw shaft while stillpermitting positive pushing and pulling of said piston during axialinward and outward movement of said ball screw shaft.
 20. Injectionapparatus for injecting a fluid into the vascular system of a mammalcomprising a syringe assembly including a syringe barrel containing apiston, means mounting said piston for axial movement within saidsyringe barrel for expelling fluid therefrom, and a main support housingfor said syringe assembly, said main support housing having an elongatedtube projecting therefrom, and a control assembly for controlling theoperation of said syringe assembly, said elongated tube extending intosaid control assembly, said control assembly including a support havingan opening therethrough in which said tube is slidably received topermit both longitudinal and rotational movement of said syringeassembly relative to said control assembly, a pair of spaced apart stoprods mounted within said control assembly paralleling said tube adjacentopposite sides thereof, a stop screw on the distal end of said tubeengageable with said stop rods to limit the rotation of said tube inopposite directions for all longitudinal adjusted positions of saidsyringe assembly relative to said control assembly, and means forclamping said syringe assembly in the desired longitudinal androtational adjusted positions.
 21. The apparatus of claim 20 whereinsaid means for clamping said syringe assembly in the desiredlongitudinal and rotational adjusted positions comprises a lock knob onsaid control assembly, a flexible collar surrounding said tube, and arod extending from said lock knob and having threaded engagement withsaid collar for loosening and tightening said collar on said tube byrotation of said lock nut in opposite directions.
 22. The apparatus ofclaim 20 further comprising a weight attached to said syringe assemblyfor locating the center of gravity of said syringe assembly closelyadjacent the axis of rotation of said tube to facilitate rotation of thesyringe assembly to any desired adjusted position.
 23. The apparatus ofclaim 20 further comprising a support stand for said control assembly,and means mounting said control assembly on said support stand forvertical movement to provide for adjustment of the vertical height ofthe control assembly and syringe assembly connected thereto.
 24. Theapparatus of claim 20 wherein said means for moving said piston axiallywithin said syringe barrel includes an electric motor for driving saidpiston, and clutch means for transmitting power from said motor to saidpiston to protect against damage if said piston bottoms out and limitpressure developed.
 25. The apparatus of claim 24 further comprising asyringe housing surrounding said syringe barrel, means for releasablymounting said syringe barrel within said syringe housing, and means forelectrically isolating said syringe barrel from said syringe housing.26. The apparatus of claim 25 wherein said syringe housing includes agear box containing drive mechanism for driving said piston by saidmotor, said syringe housing being attached to said main housing toprovide a cover for said gear box.